Internal combustion engines such as diesel engines, gasoline engines, and gaseous fuel-powered engines combust a mixture of fuel and air to generate a mechanical power output that can be used in many different ways for a variety of purposes. Unfortunately, conventional engines are inefficient and much of the energy of the fuel is wasted in the form of heat. For example, heat can be generated during compression of combustion air directed into the engine or during pumping of fluids (e.g., fuel, air, lubricant, etc.) through the engine. Additional heat is generated directly from combustion of the fuel and air, and is transferred to the engine block and to fluids (oil, coolant, exhaust, etc.) circulating through the engine. Most of this heat energy is generally discharged or otherwise dissipated to the environment.
In addition to efficiency losses associated with heat generation, extra energy must be expended to protect components of the engine from the heat and/or to keep performance of the engine from declining due to the heat. For example, the inlet air must be chilled, coolant must be circulated through the engine block, engine oil must be cooled, and exhaust temperatures may need to be lowered in order to adequately protect the engine and/or to ensure desired engine performance. Each of these actions requires extra energy, which reduces the mechanical power output of the engine and further lowers its efficiency.
One attempt to recover heat energy for an engine is disclosed in U.S. Patent Publication 2012/0023946 of Ernst et al. that published on Feb. 2, 2012 (“the '946 publication”). Specifically, the '946 publication discloses a diesel engine equipped with an Organic Rankine Cycle system (ORCS). The ORCS includes one or more boilers disposed in series or parallel that are configured to receive heat from an exhaust gas recirculation (EGR) loop and from charge air. The boilers are adapted to transfer the heat to a working fluid to vaporize the fluid. The ORCS also includes a turbine fluidly coupled to the boilers and adapted to covert energy in the vaporized working fluid to electricity, a condenser adapted to receive the working fluid from the turbine and condense the working fluid, and a pump adapted to move the working fluid from the condenser into the boilers. The ORCS also includes a recuperator adapted to transfer heat remaining in the working fluid at a location downstream of the turbine to the working fluid at a location upstream of the boilers. With this system, some of the otherwise wasted heat from the diesel engine can be recovered.
Although the ORCS of the '946 publication may improve engine efficiency through heat recovery, it may still be less than optimal. In particular, the series location of the recuperator relative to the boiler(s) may result in a reduced amount of thermal transfer to the working fluid and, hence, a reduced amount of recovered energy.
The energy recovery arrangement of the present disclosure solves one or more of the problems set forth above and/or other problems of the prior art.